The invention relates to a heat protection hood for heated rolls, in particular rapidly running rolls in paper machines.
For increasing the smoothness of paper it is often necessary to use heated rolls in the smoothing or glazing mechanism. The surface temperatures of over 200.degree. C. which are sometimes necessary result in correspondingly high heat losses through convection and radiation.
It is possible to substantially reduce the radiation losses through the use of known protective hoods with thermal isolation. However, the convection which then predominates as a result of the rolls being made to rotate ever more rapidly cannot be effectively countered. Environmental air is sucked in at one side of the protective hood is drawn along by the roll and is blown out again at the other side in the heated state.
Allround sealing also does not lead to any significant improvement as a result of the surface wear and also the pressure conditions which thereby build up. In addition to this comes the fact that the heat loss promoted by the pressure differences over the end faces of the roll lead to a non-uniform temperature profile along the length of the roll.